Eric Allam
954ee5c572
## Summary When the realtime runs feed (the backend behind the `realtimeBackend` feature flag) hydrates a change from a Postgres read replica, the read can race the replica's apply of the very write that triggered it. The delivered row then carries the previous change's content, and an isolated final change (for example a last `metadata.set` before a run goes quiet) is not corrected until the roughly 20 second backstop poll. Measured against a replica with deliberate apply delay, every delivery trailed exactly one change behind and a final change stranded for the full backstop interval. ## Fix Publishers stamp each change record with the committed row's `updatedAt`, taken from writes they already perform, so the stamp costs no extra queries. The router delays its wake hydrate until the replica's measured lag has passed, anchored to that timestamp: a record that has already spent longer than the lag in transit is hydrated immediately, so only the racing leading edge ever waits. After hydrating, a tripwire compares each row against its record's watermark. Still-stale rows are withheld and retried briefly, and each detection feeds the lag estimate. If retries run out, the rows are delivered anyway (liveness over freshness) and follow-up re-hydrates emit the fresh version through the normal working-set diff once the replica catches up, with the backstop as the terminal net. Replica lag is sampled reader-side only, and only while feeds are active. Aurora reports live lag via `aurora_replica_status()`; vanilla Postgres can only report "caught up or not" (mid-apply lag is not honestly measurable from a replica), so tripwire observations floor the estimate there. Deployments without a replica resolve to zero lag and skip the gate entirely. Tunables live under `REALTIME_BACKEND_NATIVE_REPLICA_LAG_*`, and `realtime_native.stale_hydrates` plus `realtime_native.replica_lag_estimate_ms` make replica health observable. Two adjacent fixes: a metadata update that writes nothing no longer publishes a change record, and buffered parent and root metadata operations now publish when the flusher writes them, so those changes wake live feeds instead of waiting for the backstop. For local testing, `docker-compose` gains an opt-in `database-replica` service (compose profile `replica`) with a configurable `recovery_min_apply_delay`, which reproduces replica-lag behavior deterministically. With the gate disabled this rig reproduces the one-change-behind delivery exactly; with it enabled, deliveries arrive with current content at roughly the true replica lag, across write rates faster and slower than the lag itself.
Build and deploy fully‑managed AI agents and workflows
Website | Docs | Issues | Example projects | Feature requests | Public roadmap | Self-hosting
About Trigger.dev
Trigger.dev is the open-source platform for building AI workflows in TypeScript. Long-running tasks with retries, queues, observability, and elastic scaling.
The platform designed for building AI agents
Build AI agents using all the frameworks, services and LLMs you're used to, deploy them to Trigger.dev and get durable, long-running tasks with retries, queues, observability, and elastic scaling out of the box.
-
Long-running without timeouts: Execute your tasks with absolutely no timeouts, unlike AWS Lambda, Vercel, and other serverless platforms.
-
Durability, retries & queues: Build rock solid agents and AI applications using our durable tasks, retries, queues and idempotency.
-
True runtime freedom: Customize your deployed tasks with system packages – run browsers, Python scripts, FFmpeg and more.
-
Human-in-the-loop: Programmatically pause your tasks until a human can approve, reject or give feedback.
-
Realtime apps & streaming: Move your background jobs to the foreground by subscribing to runs or streaming AI responses to your app.
-
Observability & monitoring: Each run has full tracing and logs. Configure error alerts to catch bugs fast.
Key features:
- JavaScript and TypeScript SDK - Build background tasks using familiar programming models
- Long-running tasks - Handle resource-heavy tasks without timeouts
- Durable cron schedules - Create and attach recurring schedules of up to a year
- Trigger.dev Realtime - Trigger, subscribe to, and get real-time updates for runs, with LLM streaming support
- Build extensions - Hook directly into the build system and customize the build process. Run Python scripts, FFmpeg, browsers, and more.
- React hooks - Interact with the Trigger.dev API on your frontend using our React hooks package
- Batch triggering - Use batchTrigger() to initiate multiple runs of a task with custom payloads and options
- Structured inputs / outputs - Define precise data schemas for your tasks with runtime payload validation
- Waits - Add waits to your tasks to pause execution for a specified duration
- Preview branches - Create isolated environments for testing and development. Integrates with Vercel and git workflows
- Waitpoints - Add human-in-the-loop judgment at critical decision points without disrupting workflow
- Concurrency & queues - Set concurrency rules to manage how multiple tasks execute
- Multiple environments - Support for DEV, PREVIEW, STAGING, and PROD environments
- No infrastructure to manage - Auto-scaling infrastructure that eliminates timeouts and server management
- Automatic retries - If your task encounters an uncaught error, we automatically attempt to run it again
- Checkpointing - Tasks are inherently durable, thanks to our checkpointing feature
- Versioning - Atomic versioning allows you to deploy new versions without affecting running tasks
- Machines - Configure the number of vCPUs and GBs of RAM you want the task to use
- Observability & monitoring - Monitor every aspect of your tasks' performance with comprehensive logging and visualization tools
- Logging & tracing - Comprehensive logging and tracing for all your tasks
- Tags - Attach up to ten tags to each run, allowing you to filter via the dashboard, realtime, and the SDK
- Run metadata - Attach metadata to runs which updates as the run progresses and is available to use in your frontend for live updates
- Bulk actions - Perform actions on multiple runs simultaneously, including replaying and cancelling
- Real-time alerts - Choose your preferred notification method for run failures and deployments
Write tasks in your codebase
Create tasks where they belong: in your codebase. Version control, localhost, test and review like you're already used to.
import { task } from "@trigger.dev/sdk";
//1. You need to export each task
export const helloWorld = task({
//2. Use a unique id for each task
id: "hello-world",
//3. The run function is the main function of the task
run: async (payload: { message: string }) => {
//4. You can write code that runs for a long time here, there are no timeouts
console.log(payload.message);
},
});
Deployment
Use our SDK to write tasks in your codebase. There's no infrastructure to manage, your tasks automatically scale and connect to our cloud. Or you can always self-host.
Environments
We support Development, Staging, Preview, and Production environments, allowing you to test your tasks before deploying them to production.
Full visibility of every job run
View every task in every run so you can tell exactly what happened. We provide a full trace view of every task run so you can see what happened at every step.
Getting started
The quickest way to get started is to create an account and project in our web app, and follow the instructions in the onboarding. Build and deploy your first task in minutes.
Useful links:
- Quick start - get up and running in minutes
- How it works - understand how Trigger.dev works under the hood
- Guides and examples - walk-through guides and code examples for popular frameworks and use cases
Self-hosting
If you prefer to self-host Trigger.dev, you can follow our self-hosting guides:
- Docker self-hosting guide - use Docker Compose to spin up a Trigger.dev instance
- Kubernetes self-hosting guide - use our official Helm chart to deploy Trigger.dev to your Kubernetes cluster
Support and community
We have a large active community in our official Discord server for support, including a dedicated channel for self-hosting.
Development
To setup and develop locally or contribute to the open source project, follow our development guide.